The effect of dental chair light exposure duration on shear bond strength of orthodontic brackets : an in vitro study

The purpose of this study is to determine if the duration of exposure to the halogen overhead dental chair light has an effect on shear bond strength (SBS) of metal orthodontic brackets. One hundred twenty extracted human lower incisor teeth were divided into six groups (n=20/group). Each group was assigned a predetermined duration of exposure to the halogen dental chair light, set at a fixed distance, before being cured. Light exposure times of 0 minutes (Group 1-Control), 1 minute (Group 2), 2.5 minutes (Group 3), 5 minutes (Group 4), 10 minutes (Group 5), and 15 minutes (Group 6) were tested. Each tooth was subjected to an exclusion criteria examination, scrubbed of all debris, and imbedded in a PVC-stone fixture with the crown of the tooth exposed above the stone surface. All groups had orthodontic brackets bonded with the same materials and process, then light cured for 6 seconds using the Valo LED curing unit after their designated light exposure time. Groups were tested using an Instron E-1000 universal testing machine with a shear load test set at a speed of 1mm/min using a knife-edged chisel. Data was analyzed using a one-way ANOVA test. The Adhesive Remnant Index (ARI) was scored under 10x magnification. The ARI data was analyzed using the Chi-square test (p-value < 0.05). All control and experimental groups for each specific tooth type tested resulted in SBS within or above the clinically acceptable range. Statistically significant differences (p<.05) were found between the control and experimental groups for dental chair light exposure times of 5 minutes, 10 minutes and 15 minutes. A chi-square test determined that there was statistical significance when evaluating the frequency of ARI scores when light exposure duration was greater than 5 minutes. It can be concluded that dental chair light exposure in the 5 minute, 10 minute and 15 minute groups produced higher shear bond strength than those of the control, 1 minute and 2.5 minute groups. The dental chair light is capable of initiating polymerization and causing higher bond strengths than the clinical acceptability of 5.8-7.9 MPa, thus continued dental chair light exposure over 5 minutes is not recommended. The ARI analysis revealed that as bond strength increased, the fracture pattern shifted from most remaining adhesive attached to the tooth toward that attached to the bracket

Developing Extension Professionals to Develop Extension Programs: A Case Study for the Changing Face of Extension

Development of Cooperative Extension programs depends upon the skills and abilities of competent Extension professionals. The most effective manner of building program development competencies in these Extension professionals is through professional development. A wide variety of competencies are necessary for Extension professionals to develop programs, including strong interpersonal skills. Differences exist between the professional development efforts of Extension institutions and are highlighted herein. Major challenges to delivery of professional development include time and budget, but these can be overcome through planning and innovation and use of online or hybrid methods. Professional development for program development is essential to furthering Extension’s mission, especially during times of rapid change

Is climate sensitivity related to dynamical sensitivity? A Southern Hemisphere perspective

This study examines whether the spread in the climate sensitivity of Coupled Model Intercomparison Project Phase 5 (CMIP5) models also captures the spread in the Southern Hemisphere dynamical response to greenhouse gas forcing. Three metrics are proposed to quantify the “dynamical sensitivity” of the Southern Hemisphere: the poleward expansion of the Hadley circulation, the poleward expansion of the subtropical dry zone, and the poleward shift of the midlatitude jet. In the CMIP5 abrupt 4 × CO₂ integrations, the expansion of the Hadley circulation is well correlated with climate sensitivity in all seasons; in contrast, the shifts in the subtropical dry zone and midlatitude jet are significantly correlated with climate sensitivity only in summer and fall. In winter, those responses are more strongly linked to the control climatology in each model. Thus, a narrow focus on traditional climate sensitivity alone might miss out on important features of the atmospheric circulation's response to increasing greenhouse gases, particularly in the extratropics

Evaluation of Restaurant Menus to Determine the Availability of Healthy Food Options and Guide Community Transformation Grant Activities in Massachusetts

INTRODUCTION. The availability of healthy menu options in restaurants is an important factor in the prevention of obesity. The Mass in Motion Initiative and two Community Transformation Grant (CTG) projects are conducting statewide longitudinal surveys to determine the availability of healthy food in restaurants in the state of Massachusetts. METHODS. The Community Nutrition Environment Evaluation Data System-Restaurant (C-NEEDS-R) was developed for food environment surveillance. C-NEEDS-R takes into account seasonal and geographic variations in food supplies, cultural relevance, and USDA dietary recommendations. Between summer 2012 and winter 2013, 506 restaurants in 36 Massachusetts towns and cities were surveyed and analyzed. Through menu and site evaluation, the availability of healthy entrees was examined for each restaurant, and the total number of healthy entrees as well as the percent of healthy entrees was calculated for each restaurant. For each municipality, the average number and average percentage of healthy entrees for restaurants within the community was also calculated. RESULTS. The surveyed restaurants had average 3.2 healthy entrees on the menu, accounting for 13.4% of the total number of entrees available. The percentage of healthy options varied widely by restaurant and restaurant type, ranging from 0 to 84%, and only 15 of the 506 surveyed restaurants ( DISCUSSION. As noted, menu evaluation demonstrated that the large majority of the surveyed restaurants had few healthy entrees, indicating a need to increase availability of healthy options. Analysis of restaurant- and community-level variations in availability is useful for CTG programs to formulate and prioritize interventions. Future longitudinal surveys of food stores in the intervention and control communities will help evaluate the effectiveness of CTG interventions